/*
 * Created on Oct 23, 2007
 * Created by Paul Gardner
 * Copyright (C) Azureus Software, Inc, All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 */

package com.aelitis.azureus.core.peermanager.control.impl;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Random;

import org.gudy.azureus2.core3.util.AEMonitor;
import org.gudy.azureus2.core3.util.Debug;
import org.gudy.azureus2.core3.util.SystemTime;

import com.aelitis.azureus.core.peermanager.control.PeerControlInstance;
import com.aelitis.azureus.core.peermanager.control.SpeedTokenDispenser;
import com.aelitis.azureus.core.stats.AzureusCoreStatsProvider;

public class PeerControlSchedulerBasic extends PeerControlSchedulerImpl implements AzureusCoreStatsProvider {
    private Random random = new Random();

    private Map<PeerControlInstance, instanceWrapper> instance_map = new HashMap();

    private List<instanceWrapper> pending_registrations = new ArrayList<instanceWrapper>();

    private volatile boolean registrations_changed;

    protected AEMonitor this_mon = new AEMonitor("PeerControlSchedulerBasic");

    private final SpeedTokenDispenserBasic tokenDispenser = new SpeedTokenDispenserBasic();

    private long latest_time;
    private long last_lag_log;

    protected void schedule() {
        SystemTime.registerMonotonousConsumer(new SystemTime.TickConsumer() {
            public void consume(long time) {
                synchronized (PeerControlSchedulerBasic.this) {

                    PeerControlSchedulerBasic.this.notify();
                }
            }
        });

        List<instanceWrapper> instances = new LinkedList<instanceWrapper>();

        long tick_count = 0;
        long last_stats_time = SystemTime.getMonotonousTime();

        while (true) {

            if (registrations_changed) {

                try {
                    this_mon.enter();

                    Iterator<instanceWrapper> it = instances.iterator();

                    while (it.hasNext()) {

                        if (it.next().isUnregistered()) {

                            it.remove();
                        }
                    }

                    for (int i = 0; i < pending_registrations.size(); i++) {

                        instances.add(pending_registrations.get(i));
                    }

                    pending_registrations.clear();

                    registrations_changed = false;

                } finally {

                    this_mon.exit();
                }
            }

            latest_time = SystemTime.getMonotonousTime();

            long current_schedule_count = schedule_count;

            for (instanceWrapper inst : instances) {

                long target = inst.getNextTick();

                long diff = latest_time - target;

                if (diff >= 0) {

                    tick_count++;

                    inst.schedule(latest_time);

                    schedule_count++;

                    long new_target = target + SCHEDULE_PERIOD_MILLIS;

                    if (new_target <= latest_time) {

                        new_target = latest_time + (target % SCHEDULE_PERIOD_MILLIS);
                    }

                    inst.setNextTick(new_target);
                }
            }

            synchronized (this) {

                if (current_schedule_count == schedule_count) {

                    wait_count++;

                    try {
                        long wait_start = SystemTime.getHighPrecisionCounter();

                        wait(SCHEDULE_PERIOD_MILLIS);

                        long wait_time = SystemTime.getHighPrecisionCounter() - wait_start;

                        total_wait_time += wait_time;

                    } catch (Throwable e) {

                        Debug.printStackTrace(e);
                    }

                } else {

                    yield_count++;

                    Thread.yield();
                }
            }

            long stats_diff = latest_time - last_stats_time;

            if (stats_diff > 10000) {

                // System.out.println( "stats: time = " + stats_diff + ", ticks = " + tick_count + ", inst = " + instances.size());

                last_stats_time = latest_time;

                tick_count = 0;
            }
        }
    }

    public void register(PeerControlInstance instance) {
        instanceWrapper wrapper = new instanceWrapper(instance);

        wrapper.setNextTick(latest_time + random.nextInt(SCHEDULE_PERIOD_MILLIS));

        try {
            this_mon.enter();

            Map<PeerControlInstance, instanceWrapper> new_map = new HashMap<PeerControlInstance, instanceWrapper>(instance_map);

            new_map.put(instance, wrapper);

            instance_map = new_map;

            pending_registrations.add(wrapper);

            registrations_changed = true;

        } finally {

            this_mon.exit();
        }
    }

    public void unregister(PeerControlInstance instance) {
        try {
            this_mon.enter();

            Map<PeerControlInstance, instanceWrapper> new_map = new HashMap<PeerControlInstance, instanceWrapper>(instance_map);

            instanceWrapper wrapper = new_map.remove(instance);

            if (wrapper == null) {

                Debug.out("instance wrapper not found");

                return;
            }

            wrapper.unregister();

            instance_map = new_map;

            registrations_changed = true;

        } finally {

            this_mon.exit();
        }
    }

    public SpeedTokenDispenser getSpeedTokenDispenser() {
        return (tokenDispenser);
    }

    public void updateScheduleOrdering() {
    }

    protected class instanceWrapper {
        private PeerControlInstance instance;
        private boolean unregistered;

        private long next_tick;

        private long last_schedule;

        protected instanceWrapper(PeerControlInstance _instance) {
            instance = _instance;
        }

        protected void unregister() {
            unregistered = true;
        }

        protected boolean isUnregistered() {
            return (unregistered);
        }

        protected void setNextTick(long t) {
            next_tick = t;
        }

        protected long getNextTick() {
            return (next_tick);
        }

        protected String getName() {
            return (instance.getName());
        }

        protected void schedule(long mono_now) {
            if (mono_now < 100000) {

                Debug.out("eh?");
            }

            if (last_schedule > 0) {

                if (mono_now - last_schedule > 1000) {

                    if (mono_now - last_lag_log > 1000) {

                        last_lag_log = mono_now;

                        System.out.println("Scheduling lagging: " + (mono_now - last_schedule) + " - instances=" + instance_map.size());
                    }
                }
            }

            last_schedule = mono_now;

            try {
                instance.schedule();

            } catch (Throwable e) {

                Debug.printStackTrace(e);
            }
        }
    }
}
